Limit stop for variable pitch propellers



Dec. 4, 1951 c. H. ZIMMERMAN 2,577,055

LIMIT STOP FOR VARIABLE PITCH PROPELLERS Filed Nov. 7, 1945 56 2 SHEETS-SHEET 1 .Fig. i

INVENTOR Charles Mllmma mam 73 l d/344M ATTOR N EY Dec. 4, 1951 C. H. ZIMM ERMAN LIMIT STOP FOR VARIABLE PITCH PROPELLERS 2 SHEETS-SHEET 2 Filed NOV. 7, 1945 INVENTOR.

Charles H. Zimmerman ATTQ RN EX Patented Dec. 4, 1951 LIMIT STOP FOR VARIABLE PITCH PROPELLERS Charles H. Zimmerman, Nichols, Ccnn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application November 7, 1945, Serial No. 627,126

11 Claims. 1

This invention relates to aircraft propellers and particularly to propellers having blades pivotally mounted on the propeller hub for coning and flapping movements.

One of the objects of the invention is to provide a propeller of this general type in which the cyclic loads of the several blades are in- A still further object is generally to improvethe construction and performance of aircraft propellers.

These and other objects and advantages of the invention will be apparent from the following detailed description of one embodiment thereof shown in the accompanying drawings which are submitted for purposes of illustration only.

In these drawings,

Fig. 1 is a sectional elevation taken through a propeller embodying the invention, parts of the structure which are conventional being shown in phantom or broken away to facilitate illustration;

Fig. 2 is a section on line 2-2 of Fig. 1 showing the hub and portions of the blades in front, elevation; and

Fig. 3 is a detail on an enlarged scale of a rod coupling.

As herein shown, the propeller hub is mounted in a usual manner by means of opposed wedges I 2, M and a clamping nut IE on a propeller shaft I8 which may be driven by the crankshaft of an engine or an extension thereof. The hub It has a forward outstanding annular flange 20 which is secured by means of bolts (not shown) to a like flange 22 of an extension of the propeller shaft, or sleeve 24.

The sleeve 24 carries stop mechanism generally indicated at 25 for limiting the coming and flapping movement of the propeller blades as hereinafter described and at its forward end carries an outer annular spinner supporting web 26 and an inner telescoping extension tube 28 which forms the axial support for the front end of the spinner section 30. The aft section 32 of the spinner has three apertures 34 therein at equally spaced points about its periphery through which the propeller blades 36 extend, these apertures having suflicient fore and aft dimensions to permit the blades to have a limited fore and aft movement relative to the spinner about transverse pivot pins 38 by which the blades are pivoted to the hub Ill. Each propeller blades has a housing 40 enclosing its shank which has an integral axial yoke portion 42 straddling a radial boss on the propeller hub ii) in which the pin or bolt 38 is journaled. Thus, on the pins 38 which are positioned at right angles to the axis of shaft I8, the blades are allowed to flap, i. e., move in fore and aft directions in radial planes passing through the axis of shaft IS. The position of the pivotal connection transverse the axis of shaft [8, by which the yoke of blade shank 42 is pinned to the boss on the propeller hub by pivot pin 38 prevents any side motion of blade 36.

The blades may be ground-adjustable in the housings 40 to vary the pitch of the blades in a well-known manner or, if desired, the pitch of the blades may be automatically varied in any of the well-known ways.

In accordance with the present invention, the fore and aft movements of the blades about their pivot pins 38 are controlled and limited in an improved manner by mechanism 25 so that the usually large cyclic load which acts unfavorably upon the propeller shaft is integrated into a steady force applied to the propeller shaft without the harmful stresses previously applied to the shaft and without setting up undesirable vibration. 1

In Fig. 1 the connection between mechanism 25 and one of the blades is shown. The connections of the other two blades are identical. The blade is provided with a two-partv annular collar the opposed parts of which are connected by bolts 46 which clamp the collar rigidly to the exterior of the blade housing. A yoke 48 is provided about the forward part of the collar and is pivoted relative thereto on diametrically disposed pivots 5!], parallel with the blade pivots 38. The free end of the yoke is pivotally connected to a forwardly directed connecting rod 52 by means of a bolt 54 which is radially disposed relative to the propeller shaft I8. At its forward end the rod 52 of each propeller blade assembly is connected by a universal joint including the pivot 55 between the bifurcated ears 56 of an annular plate member ber stop member 86.

58 mounted on the extension sleeve 24. This connection, as is shown most clearly in Fig. 3, not only allows the plate 58 to move fore and aft due to flapping of the blade connected by it, but also permits a limited movement of the plate about a radial axis including the ears 56 due to flapping of one of the adjacent blades.

As shown most clearly in Fig. 1, the sleeve 24 has an internally channel-shaped annular connecting member 69 freely slidable longitudinally over its central portion and this member carries and separates or spaces apart two metal rings 62 and 64 which are bolted to opposite end faces of the channel member by a plurality of peripherally arranged bolts 65. These rings have radial hub portions 5?, 67a and diverging side walls 61b. 610 which terminate in right angle inwardly directed flanges 68 to provide annular confronting recesses for the reception of annular abutment members H1 and 12, these abutment members being of rubber or other resilient material and having a thickness which is somewhat greater than the length of the flanges 68 for reasons hereinafter pointed out.

The plate member 58 is slightly tapered inwardly and is provided with a central annular recess 14 at its inner periphery in which a resilient ring 15, which may be of rubber or like resilient material, is closely received and is fixed by a series of peripherally arranged rivets it. It will be noted that the plate member 58 has its inner periphery slightly spaced from the back of the annular channel member '60 and that the ring 15 projects inwardly beyond the inner periphery of the plate member and seats on the annular member 60 along which it is slidable within the limits imposed by the abutment members and 72.

Means are also provided to limit the fore and aft sliding movement of the assembly including lar resilient stop member 86. The nut 84 is held in adjusted position by means of a 0 spring 88 having a radial end portion thereof receivable in aligned holes in the nut and the threaded portion of the sleeve. The lengths of the connecting rods 52 and yokes 48 are such that when the i blades 36 are normal to the propeller shaft the hub portion of ring 62 is somewhat closer to its stop ring 82 than the hub of ring 64 is from stop ring 86., thus permitting a greater angle of coning in the forward direction than in the aft direction.

In operation, upon a coning movement of the blades, by which is meant an equal fore or aft movement of all the blades in unison, the plate .58 with its pivot ring will slide freely along the separating member 6!] until its inner periphcry-engages abutment member 10 or 12, as the case may be. Assuming'a forward coning movement resulting in this initial engagement of plate 58 with abutment member 72, further coning movement will cause the assembly including the rings 62, 64 and the separating member 60 to move along the sleeve 26 until hub portion 61a of ring 64 comes into engagement with rub- Further coning movement causes a certain amount of compression of the rubber abutment member 12 to take place over its entire area. The abutment member 12 yields at first relatively easily but its resistance to compression gradually builds up as a result of the confining influence of the flange $8 on the rubber frustrum. The annular ring is simply placed in compression over its entire area as it is engaged by the ring 54. A rearward coning movement will bring the plate 58 into engagement with abutment member H1 and the hub 6? into engagement with resilient stop 82 in a similar manner, it being noted that a shorter axial movement is required in this direction to effect engagement with stop 82.

The cyclic loads imposed upon the individual blades result in an additional flapping movement of the blades, by which is meant the aft movement of one blade while the other blades move forward, or vice versa. Such flapping movement is resisted by the resilient abutment members 10, 12 in compression, each blade 58 during this movement assuming successively angles other than to the propeller shaft axis as the blades successively flap. These various angular positions of the blade 58 are permitted by reason of its mounting on the resilient ring '75, this ring providing in effect a resilient pivotal support for the plate permitting a limited degree of universal movement of the plate about the propeller shaft axis during the flapping action of the blades. It will be evident that during engagement of the plate 58 with the abutment members 10, .12 a greater deformation of the resilient material thereof can take place as a result .of flapping movement of the blades than is possible during coning movement. The engagement of plate 58 with the ends of flanges 68 places a definite limit On the deformation of the abutment members permitted during flapping movement of the blades.

As explained above, the degree of coming and flapping movement permitted in the fore and aft direction will vary with this installation. As shown, the blades are permitted to fiap freely 8 in either direction. Between 8 and 10 the plate 58 compresses the resilient abutment member against which it is bearing. The blades are limited to a maximum of 10 flapping movement by reason of the engagement of the plate with the periphery of flange 68 of the conical ring. Also as shown, the propeller blades may cone forward freely 5 from the neutral position before the plate 58 engages the conical ring. In the aft direction only 1 of coning under no load is per mitted.

It will be evident that as a result of this invention, a simple and inexpensive mechanism has been provided for controlling and limiting the flapping and coning of propeller blades. It will further be evident that as a result of the use of this mechanism the cyclic forces due to flapping of the blades are integrated into a steady force applied through the resilient abutment members to the conical rings and thence to the propeller shaft, thus eliminating undesirable vibration and bending forces otherwise applied directly to the propeller shaft. It will further be evident that the construction above been shown for purposes of illustration, it will be evident that the invention may be adapted to various types of propellers and housings, for example, sustaining rotors of helicopters, and that the specific details may be variously modified without departing from the intent or scope of the invention as defined in the following claims.

I claim:

1. In combinationwith an aircraft having a drive shaft, a hub on said drive shaft, and a rotary blade assembly adapted to be mounted on said hub having blades, each blade having a pivotal connection with said hub for permitting individual flapping movement of the blade in radial planes passing through the axis of said shaft about axes transverse to said shaft, a mechanism for limiting the flapping movements of said blades including ring members rotatable with said blades and concentric with said shaft having diverging flanges, resilient abutment members carried by the confronting faces of said diverging flanges, a plate member concentric with said shaft located between said abutment members and rockable in planes transverse to the axis of said shaft, and link means connecting each of said blades at a point remote from its said pivotal connection to said plate member at peripherally spaced points on the latter.

2. A rotary blade assembly adapted to be mounted in an aircraft having a drive shaft, a hub on said drive shaft, blades each having a pivotal connection with said hub, said pivotal connection having its axis of pivotation at right angles to the axis of said shaft for permitting individual movement of the blades in radial planes passing through the axis of said shaft, ring members rotatable with and longitudinally slidable on said shaft and concentric therewith having inclined confronting faces, a connecting member slidably mounted on said shaft for axial movement relative thereto and secured to said ring members for maintaining the same in separated relationship, resilient abutment means carried by the confronting inclined faces of said ring members, a rigid plate member concentric with said shaft and mounted for limited universal movement relative to said shaft between said abutment means including a resilient ring secured to said plate member and slidably mounted on said connecting member, link means pivotally connecting said blades at points spaced from their pivotal connections to said hub to said plate member at peripherally spaced points on the latter, and yielding stop members mounted on said shaft in the path of travel of said ring members for limiting their sliding movement along said shaft.

3. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having shanks, pivotal connections between said shanks and said hub to permit fore and aft flapping and coning movements of said blades, said pivotal connections having their axes of pivotation transverse to the axis of said shaft, and mechanism for controlling the movement of said blades about their pivotal axes in opposite directions from a neutral position in which they extend at right angles to said shaft axis including fixed stop members spaced along the axis of said shaft and rotatable with said blades, a cooperating assembly slidably mounted on said shaft and having confronting abutment members, said cooperating assembly being disposed between said fixed stop members and spaced apart therefrom when said blades are in their neutral position, and a plate member slidably mounted on said assembly between said confronting abutment members and having an operative connection with said blades at points on the latter spaced from said pivotal connections.

4. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having shanks, pivotal connections between said shanks and said hub having their axes of pivotation transverse to the axis of said shaft for permitting coning movements and individual flapping movement of said blades, a ring unit including rigidly connected flanges slidable along the axis of said shaft, resilient cushions carried by the confronting faces of said flanges, a plate member mounted on said ring unit between said cushions, link means connecting said blades at points remote from said pivotal connections to said plate member at peripherally spaced-points on the latter, and stop means on said shaft on opposite sides of and in the path of travel of said ring unit for limiting the sliding movement of said ring unit in opposite directions of movement axially of said shaft resulting from coning movements of said blades.

5. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having shanks, pivotal connections between said shanks and said hub having axes of pivotation at right angles to the axis of said shaft for permitting coning and flapping movements of the blades, means for limiting the flapping movements of said blades including an assembly coaxial with said hub having relatively spaced abutment members and a plate member supported for universal tilting movement between said abutment members, a resilient ring secured to said plate member and freely mounted on said assembly comprising the universal tilting support for said plate member, and means providing an operative connection between said plate member and the shanks of the several blades at points on the latter spaced from said pivotal connections.

6. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having shanks, pivotal connections between said shanks and said hub for permitting coning and flapping movements of said blades, said pivotal connections having their axes of pivotation transverse to the axis of said shaft, means for limiting the flapping movements of the blades including an assembly having divergent spaced apart abutment members and an intermediate plate member, a resilient ring member secured to said plate member and freely mounted on said assembly for supporting said intermediate plate member for universal tilting movement of the latter between said divergent abutment members in response to flapping of said blades, and means providing an operative connection between said intermediate plate member and the shanks of the several blades at points on the latter spaced from said pivotal connections.

7. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having shanks, pivotal connections between said shanks and said hub for permitting coning and flapping movements of said blades, said pivotal connections having their axes of pivotation at ri ht angles to the axis of said shaft, means :for limiting the flapping movements -.of said blades including a hub extension, a unit including connected abutment members slidably mounted on :said extension for axial movement thereon, a plate member between said abutment members having operative :connections with the shanks of the several blades, and ;a .fiexible support mounted on said :unit and secured to said plate :member for permitting universal tilting movement of the latter into engagement with said abutment members ,in response to flapping ;of :said blades, and means for limiting the :coning movements of said blades including stop members fixed to said hub extensionand-spaeed axially from the opposite ends :of and in the path of travel of said slidable unit in the neutral position of said blades.

8.. A rotary blade assembly adapted to be mounted on an aircraft having a drive shaft, a :hub on said drive shaft, blades having shanks, pivotal connections between said shanks and said hub for permitting cloning and flapping movements of said blades, said pivotal connections having their axes of p'ivotation at right angles to the :axis of said shaft, means for limiting the flapping movement of said blades, said means comprising an assembly mounted on said shaft :for sliding movement axially thereon and including abutment members, a connecting member secured to said abutment members for holding the same inspaced apart relationship and a plate member intermediate said abutment members having operative connections with said blade shanks at points spaced from their pivotal connections, and means for limiting the coning movement of said blades including stop members fixed on said shaft and spaced from and in the path of travel of said assembly in the neutral position of said blades.

' '9. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having their shanks pivotally mounted on said hub on axes transverse to said shaft for individual movement in radial planes passing through the axis of said shaft, ring members rotatable with said blades and concentric with said shaft having diverging flanges, a connecting member secured to said ring members for holding the same in spaced relationship, resilient abutment members carried by the confronting faces of said ring members, a plate member concentric with said shaft and located between said abutment members, a resilient ring mounted on said connecting member and secured to said plate member for permitting limited universal movement thereof, and link means connecting each of said blades at a point remote from the axis of pivotation of said blade to said plate member at peripherally spaced points on the latter.

10. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having pivotal connections at their shanks with said hub for permit- 18 ting individual movement of said blades :in radial planes passing through the axis of said shaft, said pivotal connections having their axes of pivotation at right angles to the axis of said shaft, ring members rotatable with said blades and concentric with said shaft having diverging flanges, a connecting member slidably mounted on said shaft for holding said ring members in separated relationship, resilient abutment means comprising rubber members carried by the confronting faces of said ring members, a plate member concentric with said shaft located between :said rubber members, a resilient ring freely mounted on said connecting member and secured .to said :plate member for permitting limited universal movement thereof, mutually inwardly directed peripheral flanges forming a part of said ring members for confining said rubber members and comprising stops 'for limiting the compression of said rubber members by said plate 'member, and link means connecting each of said blades at a point remote from its pivotal con- ;nection to said plate member at peripherally spaced points on the latter.

1].. A rotary blade assembly adapted to be mounted on an aircraft, a drive shaft, a hub on said drive shaft, blades having their shanks pivotally connected to said hub on axes transverse to said shaft for permitting coning and flapping movement of said blades about said axes, and mechanism for controlling the flapping movement of said blades about their axes, said mechanism including a separating member adapted to slide on said shaft, abutment members connected to opposite ends-of said separating member and rotatable with said blades, a plate member located between said spaced abutment members and likewise rotatable with said blades, a flexible mounting member slidably mounted on said separating member and supporting said cooperating plate member to provide for limited universal movement of the latter, and link means operatively connecting said plate member with said blade shanks at points spaced from the pivotal axes of the latter.

CHARLES H. ZIMMERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 216,244 Ward June 3, 1879 2,241,055 Chilton May 6, 1941 2,245,251 Chilton June 10, 1941 2,318,259 Sikorsky May 4, 1943 2,318,260 Sikorsky May 4, 1943 2,440,293 Stanley Apr. 27, 1948 2,465,703 Allenc Mar. 29, 1949 FOREIGN PATENTS Number Country Date 325,172 Italy Mar. 2, 1935 394,438 France Jan. 23., 1909 

